CN115108828B - Rare earth hafnate ceramic material and preparation method and application thereof - Google Patents
Rare earth hafnate ceramic material and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a rare earth hafnate ceramic material, a preparation method and application thereof, wherein the rare earth hafnate ceramic material has the chemical composition ((Tb) x Dy 1‑x ) 2 O 3 ) y ‑(HfO 2 ) 1‑y Wherein x is more than or equal to 0.2 and less than or equal to 0.6,0.4, and y is more than or equal to 0.6; preferably, the relative density of the rare earth hafnate ceramic material is 90-100%.
Description
Technical Field
The invention relates to a rare earth hafnate ceramic material, a preparation method thereof and application thereof in manufacturing nuclear reactor control rods and neutron shielding materials, and belongs to the field of materials.
Background
The control rod material used as the nuclear reactor needs to have higher thermal neutron absorption section, irradiation resistance, long service life and better mechanical property. The neutron absorbing materials of the control rods of the pressurized water reactor which are commonly used at present comprise boron carbide (B) 4 C) Hafnium (Hf), silver-indium-cadmium (Ag-In-Cd) alloy, dysprosium titanate (Dy) 2 O 3 -TiO 2 ) Etc. The boron carbide material has low cost and is easy to obtain, and the boron carbide material has excellent propertiesIs derived from the neutron absorption capacity of 10 Large neutron absorption cross section of the B isotope. But it has the disadvantage that 10 The B can generate alpha decay to lithium after absorbing neutrons 7 Li) and helium 4 He), while irradiation swelling caused by the release of a large amount of helium bubbles can lead to breakage of the material and metallic cladding. The neutron absorption cross sections of various isotopes of the metal hafnium are high, the physical and chemical stability is high, an envelope is not needed, and gamma rays with long half-life are not generated, so that the hafnium is used as a control rod absorber material for a long service life. Its disadvantages are complex purification and processing, high load on driving structure (density 13.31 g/cm) 3 ). The Ag-In-Cd alloy has a good absorption effect on neutrons In a wider energy range, but the Ag-In-Cd has limited absorption value, the melting point is only about 800 ℃, the accident fault tolerance requirement is difficult to meet, and the safety margin is insufficient for a high-power pressurized water reactor. Dy (Dy) 2 TiO 5 The titanate-based ceramic material has good neutron irradiation resistance and water corrosion resistance, but also has the problem of insufficient absorption value.
The neutron absorbing material of the control rod of the high-power commercial pressurized water reactor has better irradiation resistance and accident fault tolerance besides meeting the requirements of higher material absorption value and long service life. The hafnate formed by rare earth and hafnium has better performance and application prospect in terms of neutron absorption value, melting point, structural stability, irradiation resistance and the like.
At present, a plurality of element combinations with large thermal neutron absorption cross sections and low absorption value attenuation are selected as important directions for controlling the design of the bar materials.
Disclosure of Invention
For this purpose, the inventors considered terbium element (Tb 3+/4+ ) The relation between the valence and the crystal structure of the rare earth hafnate is provided as a practical ceramic material form. The conditions of realizing the fluorite-structure rare earth hafnate ceramic phase and the high-density structure are optimized, so that the conditions meet the requirements of all aspects of a nuclear reactor control rod, and the preparation process with simple process and low cost is also provided.
In one aspect, the present invention provides a rare earth hafnate ceramicThe chemical composition of the rare earth hafnate ceramic material is ((Tb) x Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Wherein x is more than or equal to 0.2 and less than or equal to 0.6,0.4 and y is more than or equal to 0.6.
In the invention, tb, dy and Hf which are naturally abundant in the rare earth hafnate ceramic material are used as neutron absorbers, and the proportion of Tb to Dy and the proportion of rare earth to Hf can be adjusted according to the design requirement of neutron absorption value. The material has high neutron absorption value, better accident fault tolerance performance and excellent mechanical property, and is an ideal nuclear reactor control rod absorber material.
Preferably, x is more than or equal to 0.5 and less than or equal to 0.6,0.4, and y is more than or equal to 0.6. In the range, the rare earth hafnate ceramic material has excellent mechanical properties.
Preferably, the relative density of the rare earth hafnate ceramic material is 90-100%, preferably 92-99.5%.
Preferably, the rare earth hafnate ceramic material also contains at least one of Al, mg, si, ca elements introduced as sintering auxiliary agent, wherein the mass total percentage of each element is less than or equal to 5%, preferably less than or equal to 2%
On the other hand, the invention also provides a preparation method of the rare earth hafnate ceramic material, which comprises the following steps:
(1) Weighing rare earth raw materials and hafnium raw materials according to stoichiometric ratio as raw material powder, and mixing to obtain mixed powder;
(2) And (3) after the obtained mixed powder is pressed and molded, sintering the mixed powder for 2 to 12 hours at 1500 to 1750 ℃ to obtain the rare earth hafnate ceramic material.
Preferably, the rare earth raw material is selected from at least one of oxide, metal, hydroxide, carbonate, sulfate, chloride and nitrate of Re element, wherein the Re element is Tb and Dy; the hafnium raw material is at least one selected from the group consisting of metallic hafnium, hafnium oxide, hafnium hydroxide, hafnium carbonate, hafnium chloride, hafnium sulfate and hafnium nitrate.
Preferably, a sintering aid is further added into the mixed powder, the sintering aid is a compound containing at least one element of Mg element, si element, ca element and Al element, and the mass of the Mg element, the Si element, the Ca element and the Al element in the sintering aid is not more than 5wt% of the total mass of the raw material powder, preferably not more than 2%. In the present invention, it is preferable that a liquid phase is formed during sintering by introducing a sintering aid (Si, mg, al, ca, etc.) having a lower melting point, thereby accelerating the diffusion process and reducing the densification barrier. Moreover, the sintering aid adopted by the invention has small neutron absorption cross section of Si, mg, al and Ca elements, and a certain concentration is allowed in the nuclear field. However, the added amount cannot obviously influence the neutron absorption value and the property of the rare earth hafnate ceramic, and cannot obviously influence the properties of the material such as compression resistance, water corrosion resistance, nuclear waste radioactivity and the like.
Preferably, the sintering aid is at least one selected from the group consisting of silica, tetraethyl orthosilicate, silicic acid, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate, calcium hydroxide, aluminum oxide, aluminum hydroxide, and aluminum carbonate.
Preferably, the mixing mode is ball milling mixing; the rotation speed of ball milling and mixing is 80-300 rpm, the time is 0.5-12 hours, and the ball milling medium is water or/and organic solvent; preferably, at least one of a binder and an antifoaming agent is also added during the ball milling mixing process; more preferably, the binder is at least one selected from the group consisting of polyvinyl alcohol, polyvinyl butyral, cellulose, terpineol and polyethylene glycol, and the addition amount is 0.5 to 5wt% of the total mass of the mixed powder, and the defoamer is at least one selected from the group consisting of glycerin, simethicone, dodecanediol and heptanediol, and the addition amount is 0.2 to 0.8wt% of the total mass of the mixed powder.
Preferably, the pressing forming mode is dry pressing forming or/and cold isostatic pressing forming; the pressure of the dry press molding is 10-80 MPa, and the pressure of the cold isostatic pressing molding is 150-300 MPa.
Preferably, the sintering atmosphere is a vacuum atmosphere, a reducing atmosphere or an inert atmosphere; the inert atmosphere is preferably argon atmosphere, and the reducing atmosphere is argon-hydrogen mixed gas.
In still another aspect, the invention also provides application of the rare earth hafnate ceramic material in preparing neutron absorbing materials and reactor control rods. In the invention, particles or grains in the obtained rare earth hafnate ceramic material are closely distributed, so that the rare earth hafnate ceramic material can be used as a neutron absorbing material to improve the linear density and the space utilization rate of a neutron absorber, and has the advantages of excellent mechanical property, high melting point, high chemical stability and the like, and can be used under extreme environmental conditions, thereby becoming the most main form of the neutron absorbing material of the control rod.
The beneficial effects are that:
(1) According to the neutron absorption nuclear characteristics of rare earth Tb, dy and Hf, the invention is designed, prepared and applied to the field of nuclear reactor control rods;
(2) The invention provides a rare earth hafnate ceramic neutron absorbing material which has a fluorite crystal phase structure, and the absorbing value and the nuclear characteristic of the material meet the requirements of a control rod with high power or long service life;
(3) The neutron absorbing material provided by the invention has the advantages of high density, good mechanical property, no gas generation compared with boron carbide, better water corrosion resistance, lower packaging requirement and more convenience in preparing a control rod;
(4) The preparation method provided by the invention has the advantages of rich raw material sources and simple and convenient process flow, and can ensure the large-scale production and application of the materials.
Drawings
FIG. 1 shows the preparation of example 1 ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 A photograph of the ceramic neutron absorbing material;
FIG. 2 shows the preparation of example 1 ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 Microstructure of the ceramic;
FIG. 3 is a sample of the preparation of example 2 ((Tb) 0.2 ,Dy 0.8 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 XRD spectrum of ceramic neutron absorbing material;
FIG. 4 is a sample of the preparation of example 4 ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 A photograph of a sample of ceramic neutron absorbing material;
FIG. 5 is a sample of the preparation of example 4 ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 Sample photographs of ceramic neutron absorbing material;
FIG. 6 is a sample of the preparation of example 5 ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 Microcosmic morphology of the ceramic material;
FIG. 7 is a schematic diagram of a method of using a rare earth hafnate ceramic cylinder as a control rod neutron absorber;
FIG. 8 shows the preparation of example 1 ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The absorption value of the ceramic control rod.
Detailed Description
The invention is further illustrated by the following embodiments, which are to be understood as merely illustrative of the invention and not limiting thereof.
In the present disclosure, the composition of the rare earth hafnate ceramic material (or rare earth hafnate ceramic neutron absorbing material) includes ((Tb) x ,Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Wherein x is more than or equal to 0.2 and less than or equal to 0.6,0.4 and y is more than or equal to 0.6. The rare earth hafnate ceramic material is a compact sintered body having a relative density of 92% or more, preferably 95% or more. In an alternative embodiment, the compressive strength of the rare earth hafnate ceramic material may be 280 to 520MPa.
In the invention, rare earth Tb, dy and Hf are used as neutron absorbers, so that the attenuation trend of neutron absorption value can be restrained. The material has high density and high neutron absorption value as ceramic. For example, a control rod assembly composed of Ag-In-Cd metal neutron absorber with a composition of Ag-80, in-15, cd-5wt.% has an absorption value about 20% lower than that of the rare earth hafnate ceramic neutron absorber material. Moreover, the melting point of Ag-In-Cd is only about 800 ℃, and the risk of melting down and failure under accident conditions exists.
In an alternative embodiment, 0.5.ltoreq.x.ltoreq.0.6 and 0.4.ltoreq.y.ltoreq.0.6, more preferably, x=0.5 and y=0.5. In this range, the rare earth hafnate ceramic material has excellent mechanical properties.
In the invention, the preparation method of the rare earth hafnate ceramic neutron absorbing material has simple process, and the prepared rare earth hafnate ceramic neutron absorbing material has a fluorite structure and does not release gas, so that the irradiation swelling of the control rod can be reduced. Meanwhile, the neutron absorption section of the transmutation product of the boron carbide is small, so that the absorption value is reduced rapidly, and the boron carbide can be used as a burnable poison. In contrast, the transmutation products of Tb, dy and Hf in the rare earth hafnate still have higher neutron absorption value, so that the service life is longer, and the transmutation products are favorable for being used as neutron absorption materials of large pressurized water reactor control rods with long refueling periods.
In one embodiment of the invention, a hafnium raw material (containing a hafnium compound) and a rare earth raw material (rare earth compound) are selected as raw material powder, and the rare earth hafnate ceramic neutron absorbing material is obtained through mixing, press forming and high-temperature sintering. The following illustrates an exemplary method for preparing the rare earth hafnate ceramic neutron absorbing material provided by the invention.
According to stoichiometric ratio (Tb x ,Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Weighing rare earth raw materials and hafnium raw materials, and mixing to obtain mixed powder. Preferably, the raw material powder is refined by mixing by adopting a ball milling process. In the ball milling process, a certain amount of liquid (water and organic solvent) is added as a ball milling medium, and auxiliaries such as a binder, a defoaming agent and the like are added, so that the particles of raw material powder are thinned and uniformly mixed, and then the mixed powder is obtained through drying. Wherein ball milling refining is carried out for 0.5 to 12 hours under the condition of the rotating speed of 80 to 300 r/min. After the end of autumn is finished, the mixture can be dried for 0.5 to 10 hours in an oven or a rotary evaporator at the temperature of 50 to 150 ℃. As an example, at least one solvent selected from ethanol, water and ethylene glycol is added during ball milling as a liquid phase, and the mixture is dried at 50-100 ℃ after ball milling to obtain mixed powder.
In alternative embodiments, the hafnium-containing compound may be selected from at least one of hafnium oxide, hafnium hydroxide, hafnium carbonate, and the like. The rare earth element-containing compound may be at least one selected from rare earth oxides, hydroxides, nitrates, and the like.
In an alternative embodiment, a sintering aid is also added to the mixed powder. The sintering aid may be at least one of the Al, mg, si, ca elements. The mass fraction of the element introduced as the sintering aid is not more than 5%, preferably not more than 2%, and in this range, the sintering density can be improved and the densification temperature can be reduced. In a preferred embodiment, the raw materials further comprise a sintering aid, which may be an aluminum, magnesium or silicon-containing compound, such as silica, ethyl orthosilicate, silicic acid, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate, calcium hydroxide, aluminum oxide, aluminum hydroxide or aluminum carbonate, for facilitating sintering.
In alternative embodiments, the binder may be selected from polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, cellulose, terpineol, and the like. The preferable mass percentage of the binder is 0.5% -5%.
And filling the mixed powder into a mould, and pressing and forming to obtain a biscuit. Wherein, the pressing forming mode can be dry pressing forming or/and cold isostatic pressing treatment. The pressure of the dry press molding can be 10-50 MPa. The pressure of the cold isostatic pressing may be 150-250 MPa.
Sintering the biscuit at high temperature to obtain the rare earth hafnate ceramic neutron absorbing material (in the form of sintered blocks). Wherein, sintering can be performed at 1500-1750 ℃ for 2-12 hours. The sintering atmosphere may be vacuum, argon or argon-hydrogen mixture or a mixture of two or more thereof, and the atmosphere is preferably vacuum or argon-hydrogen mixture.
The sintered body can be manufactured into various required shapes and specifications, such as cylinders, round bars and cubes, through post-processing treatments such as cutting, grinding and the like.
The present invention will be further illustrated by the following examples. It is also to be understood that the following examples are given solely for the purpose of illustration and are not to be construed as limitations upon the scope of the invention, since numerous insubstantial modifications and variations will now occur to those skilled in the art in light of the foregoing disclosure. The specific process parameters and the like described below are also merely examples of suitable ranges, i.e., one skilled in the art can make a suitable selection from the description herein and are not intended to be limited to the specific values described below.
Example 1: ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 Ceramic neutron absorbing material
Terbium oxide, dysprosium oxide and hafnium oxide are used as raw materials according to the molar ratio (Tb 2 O 3 +Dy 2 O 3 ):HfO 2 =0.4: 0.6 (y=0.4) terbium oxide and dysprosium oxide in a molar ratio of 0.6:0.4 (x=0.6). Ethanol is used as a ball milling medium, and zirconia grinding balls are adopted for ball milling for 6 hours at the rotating speed of 100 r/min. Polyvinyl butyral (PVB) with the mass ratio of 0.5% of the raw material powder of terbium, dysprosium and hafnium is added into the sizing agent as a binder, and then the sizing agent is dried at 80 ℃. And obtaining a biscuit after 60MPa dry pressing and 200MPa cold isostatic pressing. Sintering the biscuit at 1600 ℃ for 6 hours under the vacuum atmosphere condition to obtain the compact ceramic neutron absorbing material (figure 1). For the ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 XRD analysis of the ceramic shows that the prepared ceramic has fluorite structure. The density of the ceramic was measured by the archimedes principle using a drainage method, the relative density of which was 95.3%, and the microstructure indicated that densification was achieved from a scanning electron micrograph (fig. 2).
Example 2: ((Tb) 0.2 ,Dy 0.8 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 The ceramic neutron absorbing material takes hafnium oxide, terbium oxide and dysprosium oxide as raw materials according to the molar ratio (Tb 2 O 3 +Dy 2 O 3 ):HfO 2 =0.4: 0.6 (y=0.4) terbium oxide and dysprosium oxide in a molar ratio of 0.2:0.8 (x=0.2). Deionized water is used as a ball milling medium, and zirconia balls are adopted for ball milling for 4 hours at the speed of 200 r/min. Above thePolyvinyl alcohol (PVA) with the mass ratio of 1% is added into the slurry as a binder, and then the mixture is dried at 80 ℃. After 50MPa press molding and 220MPa cold isostatic pressing, obtaining a biscuit. Sintering is carried out for 3 hours at 1700 ℃ under the vacuum atmosphere condition, and hafnate ceramic is obtained. Obtained by water-displacement ((Tb) 0.2 ,Dy 0.8 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 The relative density of (2) was 97.1%, and the main phase structure was analyzed by X-ray diffraction to be a fluorite structure (fig. 3).
Example 3: ((Tb) 0.4 ,Dy 0.6 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The neutron absorbing material takes hafnium oxide, terbium oxalate and dysprosium oxalate as raw materials according to the mole ratio (Tb 2 O 3 +Dy 2 O 3 ):HfO 2 =0.6: 0.4 (y=0.6) terbium oxide and dysprosium oxide in a molar ratio of 0.4:0.6 (x=0.4). Ethanol is used as a ball milling medium, and hafnium oxide grinding balls are adopted for ball milling for 6 hours at the speed of 120 r/min. PVB in an amount of 0.5% by mass was added to the above slurry as a binder, followed by drying at 80 ℃. And (3) after 80MPa press molding and 200MPa cold isostatic pressing, obtaining the biscuit. Sintering the biscuit at 1650 ℃ for 5 hours under the argon atmosphere condition to obtain (Tb 0.4 ,Dy 0.6 ) 0.6 -(HfO 2 ) 0.4 The ceramic had a relative density of 97.2%. The compressive strength value is 340MPa by using a universal material testing machine.
Example 4: ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The ceramic neutron absorbing material takes hafnium oxide, terbium oxalate and dysprosium hydroxide as raw materials according to the molar ratio (Tb 2 O 3 +Dy 2 O 3 ):HfO 2 =0.6: 0.4 (y=0.6), the molar ratio of terbium oxide to dysprosium hydroxide is 0.6:0.4 (x=0.6). Ethylene glycol is used as a ball milling medium, and zirconium oxide grinding balls are adopted for ball milling for 12 hours at 150 r/min. PVB with the mass fraction of 0.5% is added to the above slurry as a binder, and then dried at 80 ℃. And (5) performing 50MPa press molding and 180MPa cold isostatic pressing to obtain a biscuit. Sintering the biscuit at 1620 ℃ for 8 hours under the condition of argon-hydrogen mixed gas atmosphere to obtain the rare earth alloyThe earth dense ceramic (fig. 4) has a relative density of 94.6%, and XRD results indicate that the ceramic particles after sintering have a high crystallinity and a fluorite phase structure (fig. 5).
Example 5: ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The ceramic neutron absorbing material takes hafnium hydroxide, terbium oxide and dysprosium oxide as raw materials according to the molar ratio (Tb 2 O 3 +Dy 2 O 3 ):HfO 2 =0.6: 0.4 (y=0.6), the mixture of terbium oxide and dysprosium oxide in the molar ratio of 0.4:0.6 (x=0.6) was added with ethyl orthosilicate (0.2% of the mass fraction of the raw material powder calculated as Si element) as a sintering aid. Deionized water is used as a ball milling medium, and zirconia grinding balls are adopted for ball milling for 6 hours at 120 r/min. PVA with a mass ratio of 2% was added as a binder to the above slurry, followed by drying at 80 ℃. And (5) performing 80MPa press molding and 250MPa cold isostatic pressing to obtain a biscuit. The green body was sintered at 1650 ℃ for 8 hours under argon atmosphere conditions to give a ceramic block with a relative density of 97.6%, and an electron scanning microscope photograph showed that only a small number of closed pores exist (fig. 6) as a microstructure of the ceramic. The material is used as neutron absorption material value and B in a control rod 4 C decreases more slowly than the change with burn-up, and therefore the absorption value is more stable as a control rod material for long-term use (fig. 7).
Example 6:
the rare earth hafnate ceramic material of this example 6 was prepared according to example 3, with the difference that: x=0.2, y=0.6.
Example 7:
the rare earth hafnate ceramic material of this example 7 was prepared according to example 3, with the difference that: x=0.3, y=0.4.
Example 8:
the rare earth hafnate ceramic material of this example 8 was prepared according to example 3, with the difference that: x=0.5, y=0.6.
Example 9:
the rare earth hafnate ceramic material of this example 9 was prepared according to example 3, with the difference that: x=0.5, y=0.5.
Example 10:
the rare earth hafnate ceramic material of this example 10 was prepared according to example 3, except that: the sintering aid is added into the raw material powder, and the content of Mg element is 0.2 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression properties is shown in table 1.
Example 11:
the rare earth hafnate ceramic material of this example 11 was prepared according to example 3, except that: the sintering aid is alumina, and the content of Al element is 0.2% of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression properties is shown in table 1.
Example 12:
the rare earth hafnate ceramic material of this example 11 was prepared according to example 3, except that: the sintering aid is added into the powder, and the content of Ca element is 0.2 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression properties is shown in table 1.
Example 13:
the rare earth hafnate ceramic material of this example 13 was prepared according to example 3, with the difference that: the sintering aid is ethyl orthosilicate, and the content of Si element is 0.2% of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression properties is shown in table 1.
Example 14:
the rare earth hafnate ceramic material of this example 14 was prepared according to example 3, with the difference that: the sintering aid is ethyl orthosilicate, and the content of Si element is 1% of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression properties is shown in table 1.
Example 15:
the rare earth hafnate ceramic material of this example 15 was prepared according to example 3, with the difference that: the sintering aid is ethyl orthosilicate, and the content of Si element is 2% of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression properties is shown in table 1.
Example 15:
the rare earth hafnate ceramic material of this example 16 was prepared according to example 3, with the following differences: the sintering aid is ethyl orthosilicate, and the content of Si element is 3% of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression properties is shown in table 1.
Comparative example 1
The process for preparing the rare earth hafnate ceramic material of this comparative example 1 is described with reference to example 1, with the difference that: x=0.8, y=0.2. As can be seen from fig. 8, the initial neutron absorption value of the material of comparative example 1 is less than that of example 1.
Table 1 shows the composition and the performance parameters of the rare earth hafnate ceramic material prepared by the invention:
| x | y | sintering aid | Sintering | Relative density/% | Compressive Strength/MPa | |
| Example 1 | 0.6 | 0.4 | - | 1600℃/6h | 95.3％ | 360 |
| Example 2 | 0.2 | 0.4 | - | 1700℃/3h | 97.1％ | 320 |
| Example 3 | 0.4 | 0.6 | - | 1650℃/5h | 97.2％ | 340 |
| Example 4 | 0.6 | 0.6 | - | 1620℃/8h | 94.6％ | 436 |
| Example 5 | 0.6 | 0.6 | Si element/0.2% | 1650℃/6h | 97.6％ | 485 |
| Example 6 | 0.2 | 0.6 | - | 1650℃/5h | 97.4％ | 521 |
| Example 7 | 0.3 | 0.4 | - | 1650℃/5h | 97.1％ | 513 |
| Example 8 | 0.5 | 0.6 | - | 1650℃/5h | 96.9％ | 417 |
| Example 9 | 0.5 | 0.5 | - | 1650℃/5h | 97.7％ | 390 |
| Example 10 | 0.6 | 0.4 | Mg element/0.2% | 1650℃/5h | 98.2％ | 442 |
| Example 11 | 0.6 | 0.4 | Al element/0.2% | 1650℃/5h | 97.8％ | 395 |
| Example 12 | 0.6 | 0.4 | Ca element/0.2% | 1650℃/5h | 98.5％ | 432 |
| Example 13 | 0.6 | 0.4 | Si element/0.2% | 1650℃/5h | 98.2％ | 459 |
| Example 14 | 0.6 | 0.4 | Si element/1% | 1650℃/5h | 99.4％ | 396 |
| Example 15 | 0.6 | 0.4 | Si element/2% | 1650℃/5h | 99.2％ | 472 |
| Example 16 | 0.6 | 0.4 | Si element/5% | 1650℃/5h | 97.6％ | 408 |
| Comparative example 1 | 0.8 | 0.2 | - | 1600℃/6h | 95.5％ | 372 |
Example 16
The embodiment discloses a neutron absorber material which can be used for a control rod, can be processed into a cylinder according to the length and the diameter required by the design of a reactor core, and is fixed inside a metal cladding by adopting multi-section splicing to form the control rod. FIG. 8 is a schematic diagram of an application of a control rod comprising a rare earth hafnate ceramic absorber 1, a cladding 2, a spring 3, a top end plug 4, and a bottom end plug 5, wherein the absorber 1 is fabricated from neutron absorbing material prepared as described in examples 1-16.
The absorber of the control rod has excellent radiation swelling resistance and radiation creep resistance. Compared with boron carbide, the boron carbide has higher absorption value, does not release gas, is convenient for packaging and has longer service life; compared with silver indium cadmium, the alloy has higher melting point and better accident tolerance performance.
Claims (13)
1. A rare earth hafnate ceramic material is characterized in that the rare earth hafnate ceramic material has the chemical composition ((Tb) x Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Wherein x is more than or equal to 0.2 and less than or equal to 0.6,0.4, and y is more than or equal to 0.6; the relative density of the rare earth hafnate ceramic material is 90-100%.
2. The rare earth hafnate ceramic material of claim 1, wherein 0.5 +.x +. 0.6,0.4 +.y +.0.6.
3. The rare earth hafnate ceramic material according to claim 1 or 2, further comprising at least one of Al, mg, si, ca elements introduced as a sintering aid, wherein the total mass content of each element is 5% or less.
4. The rare earth hafnate ceramic material according to claim 3, further comprising at least one of Al, mg, si, ca elements introduced as a sintering aid, wherein the total mass content of each element is 2% or less.
5. A method of preparing a rare earth hafnate ceramic material according to any one of claims 1 to 4, comprising:
(1) Weighing rare earth raw materials and hafnium raw materials according to stoichiometric ratio as raw material powder, and mixing to obtain mixed powder;
(2) Pressing and molding the obtained mixed powder, and sintering for 2-12 hours at 1500-1750 ℃ to obtain the rare earth hafnate ceramic material; the sintering atmosphere is vacuum atmosphere, reducing atmosphere or inert atmosphere.
6. The production method according to claim 5, wherein the rare earth raw material is selected from at least one of oxides, metals, hydroxides, carbonates, sulfates, chlorides, and nitrates of Re element, wherein Re element is Tb and Dy; the hafnium raw material is at least one selected from the group consisting of metallic hafnium, hafnium oxide, hafnium hydroxide, hafnium carbonate, hafnium chloride, hafnium sulfate and hafnium nitrate.
7. The method according to claim 5, wherein a sintering aid is further added to the mixed powder, the sintering aid is a compound containing at least one element selected from the group consisting of Mg element, si element, al element, and Ca element, and the total mass of Mg element, si element, al element, and Ca element in the sintering aid is not more than 5wt% of the total mass of the raw material powder.
8. The method according to claim 7, wherein the sintering aid is at least one selected from the group consisting of silica, tetraethyl orthosilicate, silicic acid, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate, calcium hydroxide, aluminum oxide, aluminum hydroxide, and aluminum carbonate.
9. The method according to claim 5, wherein the mixing is ball milling; the rotation speed of ball milling and mixing is 80-300 rpm, the time is 0.5-12 hours, and the ball milling medium is water or/and organic solvent.
10. The preparation method according to claim 9, wherein at least one of a binder and an antifoaming agent is further added during the ball milling mixing process, the binder being selected from at least one of polyvinyl alcohol, polyvinyl butyral, cellulose, terpineol and polyethylene glycol, and the addition amount being 0.5 to 5wt% of the total mass of the mixed powder; the defoamer is at least one of glycerol, dimethyl silicon, dodecanediol and heptanediol, and the addition amount is 0.2-0.8wt% of the total mass of the mixed powder.
11. The method according to any one of claims 5 to 10, wherein the press forming is dry press forming or/and cold isostatic press forming; the pressure of the dry press molding is 10-80 MPa, and the pressure of the cold isostatic pressing molding is 150-300 MPa.
12. The preparation method according to any one of claims 5 to 10, wherein the inert atmosphere is preferably an argon atmosphere and the reducing atmosphere is an argon-hydrogen mixture.
13. Use of the rare earth hafnate ceramic material of any one of claims 1 to 4 for the preparation of neutron absorbing materials and reactor control rods.
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| CN111646794A (en) * | 2020-05-29 | 2020-09-11 | 中国核电工程有限公司 | Neutron absorber material, preparation method thereof and control rod |
| CN111704459A (en) * | 2020-05-29 | 2020-09-25 | 中国核电工程有限公司 | Neutron absorber material, preparation method thereof and control rod |
| CN111933313A (en) * | 2020-07-21 | 2020-11-13 | 上海核工程研究设计院有限公司 | Long-life neutron absorbing material |
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| CN110818414A (en) * | 2019-09-27 | 2020-02-21 | 厦门大学 | Europium hafnate neutron absorbing material and application thereof |
| CN111646794A (en) * | 2020-05-29 | 2020-09-11 | 中国核电工程有限公司 | Neutron absorber material, preparation method thereof and control rod |
| CN111704459A (en) * | 2020-05-29 | 2020-09-25 | 中国核电工程有限公司 | Neutron absorber material, preparation method thereof and control rod |
| CN111933313A (en) * | 2020-07-21 | 2020-11-13 | 上海核工程研究设计院有限公司 | Long-life neutron absorbing material |
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